US2447159A - Lamp terminal structure and method of manufacture - Google Patents

Description

8- 17, 1948- P. o. CARTUN LAIP TERIINAL STRUCTURE AND HOD 0F WUFACTURE Filed June 19, 1944 fVI/EN 70/2: PAL/L fl [ARR/N 51 [175 A7 THRIVE) Patented Aug. 17, 1948 UNITED STATES PATENT OFFICE LAMP TERMINAL STRUCTURE AND METHOD OF MANUFACTURE Paul 0. Cartun, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application June 19, 1944, Serial No. 540,969

2 Claims; (01. 176-126) explained in connection with double-ended tubular discharge lamps of low-pressure positive column type, and particularly fluorescent lamps of this character. The lamps particularly described are of cold-starting type, having electrodes or cathodes which are heated only by the energy of the discharge current, as exemplified in one known form by U. S. Patent No. 2,114,842 to Inman, and as contrasted with the present commercial hot-starting fluorescent lamps, whose electrodes are specially preheated and rendered emissive of electrons before discharge between them is brought about, as described in U. S. Patent No. 2,212,427 to Peters. The invention aims at providing simple, strong, and eflicient structures; at facilitating the fabrication and processing of lamps; and at reducing costs. Various other features and advantages of the'invention will appear from the description of species and forms of embodiment and from the drawings.

In the drawings, Fig. 1 shows a longitudinal section through one end of a lamp constructed according to my invention; Fig. 2 is .plan view of the end unit of the lamp shown in Fig. l; and Fig. 3 is a tilted or perspective view of a lamp envelope tube and an end unit ready for being sealed to one another in accordance with the invention.

Fig. 4 is a side view, partly sectional, of an end unit difierent from that shown in Figs. 1-3; and Fig. 5 is a side view of one end of a lamp embodying the end unit shown in Fig. 4, with the end wall in section.

Fig. 6 is atilted or perspective view of one end of a lamp embodying other modifications.

Fig. 7 is a tilted view of one end of a lamp illustrating still another modification.

As shown in Figs, 1 and 2, the discharge lamp L comprises a tubular envelope in permeable to the light or other desired radiant output, and usually of vitreous material, such as the soft glass of which fluorescent tubes are commonly made. Only one end of the lamp L appears in the drawing; but in the'case of a double-ended tubular lamp, the construction shown may be substantially duplicated at the other end. The wall II that closes in the end of the envelope l0 carries a mount l2 including an electric energy translation device l3 which is here shown as an emissive cathode in the form of a coil or coiled coil of tungsten wire coated with activating oxide (5) such as an alkaline earth' mixture including barium and strontium oxides. This emissive filament I3 may be supplemented with the usual unactivated anodes l4, l4, formed by ends of the current leads |5, |6 bent to extend parallel to the coil l3 and to one' another. As here shown, the envelope end is formed primarily by a sheet metal disc to which the end of the tube I0 is sealed at IT, preferably by fusion of the material of the tube ill itself. The disc may be like those disclosed in U. S. Patents Nos. 2,146,579 to Inmanand 2,158,849 to Blake, which serve as electrical contact terminals for the devices on which they are used. The end disc H is shown as concavely dished for strength, has a narrow upturned lateral marginal flange '|8, and has a reentrant central hollow boss IQ of inverted conoidal form, which enlarges inward so as to provide an overhanging shoulder with, a peripheral groove 20 at the junction of the boss with the saucer-like concave portion of the disc. The disc may be made of the chrome-iron alloy known commercially as Allegheny 55, or of any other metal that will seal properly.

As shown in Figs. 1 and 2, the filament supporting current conductors or lead wires |5, [B of the mount l2 have suitably separated clamps 2|, 2| remote from the disc ll, between which the filament I3 is connected, while their portions nearer the disc are more closely spaced and are mechanically but. insulatively interconnected by means of a vitreous stem head 23 (which may be of glass like that of the tube I0), fused and sealed about the wires. The anodes |4, |4 may consist of extensions of the wires I5, l6 beyond the clamps 2|, 2|. Still nearer the disc H, the resilient conductor wire l5 may extend outward and downward. This wire [5 is firmly or rigidly attached and electricaly connected to the disc preferably by having its end portion bent into the form of a split ring 25 encircling and elastically gripping the boss l9, at the bottom of its peripheral groove 20. If desired, the wire ring 25 may be welded to the boss I! to provide a more perfect electrical and mechanical connection to the disc II. The other conductor wire it has an extension 24 downward and outward from beyond the insulative head 23 past the enlarged head of the boss l9 and past the disc H to the outside of the envelope ID, at or near its seal I to the disc II. The wire It (or at least its portion 24 that passes to the outside of the envelope l) should be of metal that can be sealed gas and vacuum-tight through the material that it Denetrates, such as the chrome-iron alloy of which the disc I I is made. As shown in Figs. 1, 2, and 3, the lead extension 24 is of wire much finer than the rest of the leads l5, l6, and is welded in the stouter part of lead 16 below the bead 23. The fineness of the wire 24 gives greater assurance of a satisfactory seal of this wire through the material at H. The disc ll may have a suitable opening to accommodate the wire 24: as here ,4 terminal at each end, like .the disc ll shown in Figs. 1, 2, and 3, the heating is not so easy. To heat by a discharge between the cathodes at opposite ends of a lamp requires a much longer time than when it is done by passing current through each cathode. To heat a cathode by a high-frequency coil outside .the lamp may be difi'icult or shown, the disc margin or edge is arcuately notched out at 26 to about the depth of the flange iii, to allow the wire 24 to extend through the seal material I! that attaches the disc II to the end of the tube I 0 without danger'of coming in contact with the disc.

Fig. 3 illustrates one preferred method of performing a sealing-in operation to attach the end unit comprising disc II and mount l2 to the envelope tube ID by fusion of the tube end, without the use of any other sealing material. As herevshown, the end of the tube l0 (reduced in diameter at a rounded shoulder 21 as is usual for envelope tubes of fluorescent lamps) has been brought close to the disc II in axialalignment therewith, the mount l2 extending into the tube, and the lead wire 24 extending out between the margin of the disc and the end of the tube, in or opposite the disc notch 26'. As shown in Fig. 3, the disc H is apertured through the center of the boss l9 and carries an exhaust tube 28 sealed thereto around the aperture. The disc ll being heated evenly and adequately by any suitable means (here diagrammatically represented by flames F playing on its side remote from the tube l0) the reduced end of the tube I0 is pressed against the hot disc (or vice versa) until the tube end softens and fuses and seals to the disc just inside the flange l8, whereupon the heating of the disc is discontinued to allow the glass to cool. While the end of the tube I0 is being pressed against the hot disc II to heat and fuse the tube, force is applied to the wire 24 in the direction indicated by the arrow A in Fig. 3, to shift the wire away from the disc into the softened material of the tube end, and to hold the wire away from the disc II until the material has hardened and set. This completes a fused in-seal as shown in Fig. 1, with the lead wire 24 sealed gas and vacuum-tight through the in-seal portion of the envelope wall In out of contact with the disc.

In processing many electrical devices during manufacture, it is necessary or convenient to heat their electric translation means after being sealed into the envelope of the device, as an incident of exhausting, gettering, gas-charging, or otherwise treating the device or its translation means. In the case of discharge devices, this is necessary in order to degas the electrodes; and in the case of activated cathodes, it is particularly necessary to convert or transform material that has been applied to them before sealing-in into the desired emissive material or condition, and to get rid of gas or vapor evolved in the transformation. In the case of ordinary hot-starting fluorescent lamps having a pair of current leads for each cathode, which are used in preheating the cathodes before starting the operating discharge in the lamp, these leads are available for passing heating current through the cathodes during the processing just referred to; but in the case of fluorescent lamps having but a single contact impracticable because of the fineness of many filamentary cathodes. But by providing the mount l2 with an extra lead l6 extended out at 24 through the envelope wall or end seal as described, resistance heating of the cathode by passing current through it as indicated diagrammatically in Fig. 1 becomes practicable and easy. After this has been done, the extent or projection of the external portion of the lead 24 beyond its seal may be reduced, as explained hereinafter, so that it cannot get in the way or give any trouble in a lamp socket (not shown). The lamp end may be completed by sealing off the exhaust tube 28 inside the recess afforded by the boss 19 as indicated at 3| in Fig. 1, so that the seal is well sheltered and protected in the recess.

The end unit l2 shown in Figs. 4 and 5 differs from that in Figs. 1, 2, 3 in that the edge of the disc Ila has no upturned flange I 8 as in Figs. 1-3 and no notch 26, and in that the lead "5a is of the same size as the lead [5 throughout. Also, the disc Ila is without the exhaust hole and tube 28 of Fig. 3. As shown in Fig. 4, the lead l5 extends upward on a steeper slope than in Figs. 1 and 3, so that the mount [2 is tilted to the left somewhat, and the lead I'Sa clears the disc edge by an ample distance. When, therefore, the envelope tube I0 is pressed against the disc Ila as above described in connection with Fig. 3, the lead I5 is elastically flexed to the right and downward (as Fig. 4 is drawn) by the pressure of the tube end. As the tube end softens under the heat of the disc I la, the lead l5 unfiexes elastically and pushes the lead I 6a upward and sidewise through the soft glass enough to shift or keep the lead lBa away from the edge of the disc, and the seal cools off with the mount 12 in proper position and with the lead llia out of contact with the disc edge, as shown in Fig. 5. After the lamp processing which requires use of the lead lBa to heat the translation means l3, as above described, the extent or projection of lead Ilia outside the envelope I 0 may be reduced by cutting the wire off at or close to the latter, or by bending any short protruding wire end up against the envelope wall below the shoulder 21, as shown in Fig. 5 at 32, or both.

Fig. 6 illustrates a mount l2b in which the parts are arranged differently from what is shown in Figs 1-5: i. e., the lead wire I6?) is insulatively connected to the lead wire I5b by the bead 23b directly in line with the wire l5b, instead of alongside it as in Figs. 1-5; and the alkaline earth oxide-activated filament coil cathode l3b extends axially of the envelope tube l0, instead of crosswise, being connected between clamps at the ends of lateral branches 33, 34 of the leads 15b, lBb, consisting of short wires welded to the latter. The lead wire I6b has another branch 24b that extends rearward and alongside the standard formed by wires lGb, l5b and bead 23b, and passes to the outside of the envelope II) at or adjacent the seal l1. As shown, this branch 24b is of fine wire like the lead extension 24 in Figs. 1-3, being welded at one end of the junction of wire 34 with wire "$12, and being bent (in a Z-configuration) to extend out through the envelope wall. An

anode disc b is shown arranged transversely of the envelope l coaxially therewith and in front of the translation means or filament [3b, and is connected to the inner end of the latter through the lead I62) and its branch. The disc llb may conveniently be supported by means of the lead 1 5b, which is shown as having its upper end bent to extend radially inward and welded to the rear face of the disc. To avoid having the disc ll function as anode, rather than the disc l'lb connected to disc ll through the resistance of filament 131), the disc ll may be covered wholly or nearly completely with suitable insulation. This does not necessarily mean a complete vitreous end wall for the envelope l0 inside the disc I l, or an insulative coating covering the inner side of disc I I; on the contrary, a thin disc of insulation 35 such as mica may be suitably interposed between the disc II and the cathode lib, being as shown threaded around the wire l5b to lie against the boss l9 and the envelope and disc joint 11, inside the lead wire 241).

With this arrangement, substantially the whole discharge current goes to the disc 24b and traverses' the cathod filament l3b during each anode cycle at this end of the lamp L (when the lamp is operating on A. 0.), thus heating the filament. By making the filament wire l3b of proper gauge and resistance, it can be resistanceheated in this manner on the anode cycles sufficiently to make it emit thermionically on the cathode cycles all the electrons required to carry the discharge current in the lamp L, without necessity for any heating by the discharge on the cathode cycles, although there is, generally, some current flow through at least part of the filament |3b on the cathode cycles, and some consequent resistance-heating of the filament during these cycles. By making the anode disc Nb of suitable size, the anode drop during the anode cycles can be minimized or reduced virtually to zero, thus minimizing the energy in the discharge at this time, and also eliminating voltage oscillations at the anode. For a (SO-watt fluorescent lamp H operating with a discharge current of 0.4 ampere and having a 1-inch T-8 tube 6 feet long for its envelope It), a disc Nb of 5 mil sheet molybdenum or iron about inch in diameter is satisfactory, and the filament lib may consists of 100 mm. length of tungsten wire of 1.83 mil size wound 347 turns per inch on a mandrel of 4 mil size for its primary winding; and for a coiled coil, this mandrel with its winding maybe wound 70 turns per inch on a 16.1 mil mandrel, giving about 8 turns of secondary winding. After suitable heattreatment to set the coils, both mandrels may be removed by dissolving them out as usual. With these dimensions, half the energy traverses the filament 13b on the anode cycles of the electrode.

Fig. 7 shows a mount essentially like that in Figs. l-3, but illustrates a variation from Figs. 1-6 as regards the way in which the lead wire 240 is brought out. Instead of extending past the outer disc edge It as in all of Figs 1-6, the lead 24c extends through a round hole 280 pierced in the disc H and closed by a suitable seal around the wire: in other words, the disc opening for the wire He has the form of a hole instead of a notch as in Figs. 1-3. As here shown, the hole 200 is in the disc margin near enough to the disc edge It to be covered and sealed up around the wire 24c by the material forming the end seal l1 between the tube 10 and the disc l'l when the tube end is pressed and fused to the disc as described in connection with Figs. 1-3. Thus the use of a disc opening 260 in the form of a hole need not entail any extra sealing operation, nor need any lateral pressure be exerted onthe wire 24c during the sealing as in Figs. 1-6: all that is necessary is to hold the wire centered in the hole 260 when forming the seal H.

In order to dispense with repetitive description, various parts and features in Figs. 4-7 are marked with the same reference numerals as their homologues in earlier figures, a distinctive letter being added where such distinction seems needful.

I make no claim herein for the special mount and electrode features illustrated in Fig. 6, as distinguished from those in Figs. 15, since these features of Fig. 6 form no part of my present invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An end unit for an enevolpe of the character described comprising a metal end disc, for scaling to the envelope end, having a lateral marginal flange with a notch in said flange, and a filament mounting structure carried by said disc comprising current conductors having separated filament clamps remote from the disc and also having portions nearer the disc more closely spaced, with an insulative stem bead sealed to and mechanically but insulatively interconnecting said portions of said conductors, one of said conductors being attached and electrically connected to said disc, and the other conductor extending outward past the edge of the disc opposite said notch, in position to be insulatively embedded in and extend out through an insulative seal by which said disc may be attached to an envelope end.

2. A method of fabricating an electrical device comprising a radiation-transmitting envelope with a metal end disc carrying a mount in the envelope including a resilient conductor attached and electrically connected to said disc, an associated conductor mechanically but insulatively connected to the foresaid conductor, and a filament connected between said conductors; which method comprises placing the open end of the envelope around the mount adjacent the disc, with said associated conductor extending out between the envelope end and the edge of the disc; bringing said envelope end to the disc and sealing it thereto; and pressing said outward extending associated conductor toward the enevelope end away from the disc while the seal is soft.

PAUL O. CARTUN.

REFERENCES CITED The following references are of record in the file of this patent;

UNITED STATES PATENTS Number Name Date 1,205,002 Marshall Nov. 14, 1916 1,972,125 Anderson Sept. 4, 1934 2,146,579 Inman Feb. 7, 1939 2,177,498 Payne Oct. 24, 1939 2,359,483 Kuebler Oct. 3, 1944 FOREIGN PATENTS Number Country Date 499,120 Great Britain Jan, 18, 1939

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